S 4.216 Stipulation of the system limits of z/OS

Initiation responsibility: Head of IT

Implementation responsibility: Administrator

For the operation of a z/OS system it is important to determine the system limits for the maximum loading of resources. The following notes should be observed:

Communication of system limits

The system limits, whose planning is described in safeguard S 2.286 Planning and use of zSeries systems, must be known to the administrators and application owners concerned. The system limits include the maximum size of a file, the maximum amount of main memory available, the maximum size of files for FTP (File Transfer Program) transfers, the number of LPARs (Logical Partitions) on a zSeries mainframe, the number of systems in a parallel Sysplex cluster and other similar items. System limits must be known and taken into account so as to avoid errors in the running of applications.

Magnetic tape units

The number of magnetic tape units available should be reconciled with the requirements of the relevant application owners. To avoid excessive simultaneous usage of magnetic tape units, the times at which applications access magnetic tape units must be co-ordinated among the application developers and those responsible for the applications concerned.

Hard disks

The necessary hard disk capacity must be planned and specified by the application owners. The Space Management must take care to ensure that the hard disk storage space is sufficient. If this is not the case, the relevant application owners must be informed. (For further information on the Space Management, see S 2.295 System administration of z/OS systems).

Initiators

The initiators, which are activated in JES2 (Job Entry Subsystem), control the parallel processing of batch jobs. Their number must be tailored to the hardware capabilities The number and the associated restrictions must be known to the application owners.

TSO users and address spaces

The maximum number of TSO users and the maximum number of address spaces that can be started must be tailored to the hardware capabilities.

Savings potential

The possibility of saving system resources by automatically logging off users who have been inactive for a certain time (e.g. 30 minutes) should be considered. Here it is necessary to check whether this could lead to problems with the applications operated. The users must be informed via appropriate rules.

Review questions:

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